Consider adding attoparsec to common dependencies for wordy exercise

[mike-barber]

I've been trying to submit a (locally-working) solution to the wordy exercise, but it's failing to download attoparsec due to an HttpExceptionRequest. I am submitting both package.yaml and the source.

I originally used megaparsec but ran into the same issue. The exercise itself suggests that "This is a perfect opportunity to learn some Attoparsec or Parsec!", so I figured attoparsec might be a better option given the recommendation.

I may be missing a workaround here, but from surveying recent issues it appears that packages required need to be baked into the test runner here: pre-compiled/package.yaml, c.f. test runner pr 32

library:
  exposed-modules: LeapYear
  source-dirs: src
  ghc-options: -Wall
  dependencies:
    - QuickCheck
    - lens
    - parallel
    - vector
    - split
    - random
    - string-conversions
    - text

Would the solution to this be to add attoparsec to the above, or is there another workaround I should be using?

EDIT: I've verified that adding attoparsec to the test runner image resolves the problem - tested using ./bin/run-in-docker.sh wordy ... -- still not sure if this is the preferred solution though.

[petertseng]

I checked the number of occurrences of attoparsec and megaparsec in #1006 (comment), which is the list of how many times a given package was imported in solutions as of October 2021. Given their rate of occurrence plus the fact that we have both https://github.com/exercism/haskell/blob/main/exercises/practice/wordy/.docs/instructions.append.md and https://github.com/exercism/haskell/blob/main/exercises/practice/sgf-parsing/.docs/instructions.append.md suggesting using some parser combinator library, I'm supportive of adding both attoparsec and megaparsec to https://github.com/exercism/haskell-test-runner/blob/main/pre-compiled/package.yaml. Is fine to support multiple options.

[mike-barber]

Thanks @petertseng -- I've opened a small PR for this :)

Viewing this from the perspective of a new-to-Haskell user, it is quite tricky to know what packages are viable for use in solutions.

I'm wondering whether it would be worth adding a list of them to the documentation in docs/TESTS.md, since they really have to be baked into the image to work. Although I'm not sure how to get a full list since packages pull in other ones, and there are a whole lot included in base too.

[petertseng]

I'm wondering whether it would be worth adding a list of them to the documentation in docs/TESTS.md,

That is a good idea. I think we did not do it immediately because we were waiting for some long-term thing where, upon submission, the site might be able to detect whether the student used a package that the test runner doesn't have and tell them about that. However, I'm not sure what the path to implementing that long-term solution is, so just listing them in documentation will serve for the time being. My ideas of how to do that have been put in #1045 now.

[mike-barber]

Thanks for all your help! The issue has been resolved via the linked PR.